Well drill tubing commonly is formed of long tubes that are connected together end to end to form a string. A well drill is secured to the bottom tube and a power source is connected to the uppermost tube for rotating the string for drilling within a well. As the drill progressively moves downwardly into the ground, additional tubes are coupled to the upper end of the string. For removal of the drill or for clearing of the well or for testing, etc., the string of tubes is lifted upwardly out of the well and the individual tubes are uncoupled. Thereafter, they are reinserted into the well and coupled together one by one, as they descend and the cycle is repeated.
Commonly used well drill tubes are formed of relatively expensive seamless tubes made of steel alloys suitable for this function. A typical tube could be roughly 24 feet in length with an outside diameter of 31/2 to 41/2 inches and with opposite ends that are thickened into a flange-like shape.
The thickened or flanged opposite ends are usually formed in an upsetting machine which involves holding a tube end in a die and hammering the tube ends by successive machine blows into the die cavity to form the enlarged or flanged-like ends.
After the well drill tube is formed, it is conventional to weld to its opposite ends coupling parts, that is, a threaded male coupling part on one end with a threaded female coupling on the opposite end so that each tube may be threadedly engaged with successive tubes. Conventionally, friction welding or spin welding is utilized to weld the adjacent annular ends of each coupling to the thickened end of the tube. This procedure is still followed with the improved tubing of this invention.
Because the tubes are subjected to relatively high loads from the weight of other tubes suspended below them. and also receive heavy twisting forces or torque, they must be made of relatively thick material. Then the tubes should be heat treated to handle the stresses and to provide the necessary metallurgical characteristics. The hammering action of the upsetting equipment particularly requires a follow-up heat treatment.
The invention herein relates to an improved method for forming drill tubing which improves the metallurgical characteristics of the tube for improving its strength characteristics, while permitting the use of a less expensive starting material.
A method for forming tubes by an extrusion procedure is described by my two prior patents, No. 3,837,205 issued Sept. 24, 1974, and No. 3,886,649 issued June 3, 1975 for the purpose of forming automotive axles. However, the extrusion methods disclosed in such patents have been confined to relatively short length tubes. For example, the length of an automotive vehicle axle is no more than a few feet. Forming very long tubes has been regarded as not possible. Thus, the invention herein relates to forming very long tubes, such as on the other of about 24 feet or longer, using forming blanks that could be roughly 20 feet in length.